Rotary wing aircraft



y 8, 1948. H. H. PLATT ROTARY WING AIRCRAFT Filed Jan. 25, 1939 5 Sheets-Sheet 1 INVENTOR.

ORNEY.

May 18, 1948. H. H. PLATT 2,441,920

ROTARY WING AIRCRAFT I Filed Jan. 25, 1939 5 Sheets-Sheet 2 INVENTOR.

aazk May 13, 1948. -r 2,441,92Q

ROTARY WING AIRCRAFT Filed Jan. 25, 1939 5 Sheets-Sheet 3 fl 6 60 I J I 2 j J I! y D) 5 1/ V 6 v I44 1 6'7 12 44 5 64 j 2 .55 v I J19 J52 INVENTOR.

i z: CATTORNEY.

May 18, 1948. H. H. PLATT ROTARY WING AIRCRAFT 5 Sheets-Sheet Filed Jan. 25, I939- VII/10,1177

llI/I/II villi!!! rill flunk? A 1N VENTOR.

ATTORNEY.

May 18, 1948," 5 H, H, P AT-r R 2,441,920

ROTARY WING AIRCRAFT Filed Jan. 25, 1939 5 Sheets-Sheet 5 IN VENTOR TTORNEY.

Patented May 18, 1948 ROTARY WING AIRCRAFT Haviland H.v Platt, New York, N. Y.', assignor, by

mesne assignments, to McDonnell Aircraft Corporation, St. Louis, Mo., a corporation of Maryland Application January 25, 1939, Serial No. 252,809

6 Claims.

'The present invention relates to rotative winged aircraft'and it relates .further to powerdriven rotative winged air craft in which the rotor may, at will, be power-driven to supply both vertical thrust required for sustension as torque reactions of the several rotors upon thefuselage may be balanced against each other so as to neutralize each other and thereby to make it unnecessary otherwise to counteract the torque reaction of rotors in the power-driven condition thereof. v a

One of the objects of the present invention is themattainment of substantial stability under varying flight conditions.

A further object of the present invention is to completelyneutralize torquereactions of the several rotors under all operating conditions and notwithstanding all the variants encountered in the different operating conditions.

, A further object of the present invention is to provide means whereby excessive variations in rotor speed may be prevented under different flight conditions and notwithstanding the many tions'."

A further object of the present invention is to 'provide means whereby failure of either engine or transmission will not render the aircraft uncontrollable but which will permit adequate control of the aircraft notwithstandingfailure of either engine or power transmission to either v one or several rotors.

aircraft under all flight conditions as well as on the ground.

For the purpose of illustrating the invention,

' there is shown in the accompanying drawings one form thereof whichis at present preferred, since the same has been found in practice to give satisfactory'and reliable results, although it is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrangement and organization of the instrumentalities as herein shown and described.

} variants encountered in different flight condi- In the accompanying drawings in which like reference characters indicate like parts:

Figure 1 vrepresents a top plan view of one form of rotative winged aircraft embodying the present invention.

Figure 2 represents a front elevational view of the same.

Figure 3 represents a side elevational view of the same. i V

Figure 4 represents a vertical section through the power transmitting differential gear housing and gear train in the fuselage atthe point of convergence of the two drive shafts leading to the two rotors.

Figure 5 represents a section on Figure 4. v

Figure 6 represents a section of one of the two rotor heads; one being at the outer end of each of thetwosimilar drive shafts leading to each of the two rotors. v I

Figure 7 represents a top plan view of the, rotor head shown in Figure 6. r y c v I c Figure 8 represents a schematic plan viewrof the controls of a. helicopter representing one embodiment of the present invention. V

In the embodiment of the present invention shown in the drawings, a fuselage I of suitable construction is formed with a pair ofopposite and laterally extending cantilever pylons or arms 2 and 3 generally of a hollow type suitably braced for vertical lift aswell as for fore and aft stressing as well as to resist torsional stresses. In the embodiment shown, the cantilever pylon arms 2 and 3 are covered with a continuous sheathing of the fuselage. The cantilever arms maybe formed either with the surface or skin sheathing stressed so as to contribute to the strength of the arms in one or more directions (that is, to resist vertical load or fore and aft forces or torsional forces), or the sheathing may be entirely unstressed and serving merely as a fairing to minimize the net drag of the'arms as a whole.

line 51-5 of The arms 2 and 3 may also be formed of 'a cambered cross-section to contribute some lift when the craft has substantial forward air speed, although in the embodiment here shown, the amount of lift obtainablefro-m the relative vertically projected area of the arms would be comparatively small.

The fuselage is also preferably provided with a stationary vertical tai-l surface 4 from which a movable or adjustable vertical tail surface or rudder 5 extends, being hingedly or pivotally mounted in any suitable manner. A stationary horizpntalfltail surface 6 is also preferably proe ral t rone h the vertical plane passing through the rotor hub axis or may be mounted more or less in line-with the rotor hub axis, that is, in linewiththe vertical plane passing therethrough. In the particular embodiment of the invention;.here;slflown Microngine 9 is located slightly behind such vertical plane and with its drive shaft [0 extending forwardly in a generally horizontal direction into the difierential power-transmission housing =ll located more or less ini'the vertical plane passing ,through .the ,-.r0t0r hub axis. ,From the differential transmissiondevice ;l.l,..drive shafts .l2 and J3 extend laterallyin Opposite .directions through .the cantilever arms .2 ands, respectively, .to similar rotor heads I4 and I5, oneof .which U5) is shown in detail inEigures Sand ,7,

The differential transmission housin .LI may besupportedbydirect attachment to the fuselage or to fuselage structural members, or ,it .may be fastened directly to the engine itself through be t o o h fa tenin means passing .thmu h suitable ,holes 1,6 in .one .end of the housing. In

the latterevent, .the differential transmission becomes closely coupled to the engine so that it tends {to form a single unit therewith from the.

standpoint of weight distribution and so that the engine, .together with the differential transmission a shPWl inEigures L4 and v5. m ybe cen- .tered more .or -less approximately in .the vertical plane passing through the rotor ,hub axis.

The housing .l.l may be forn'ried of two more or less similar halves alonga dividing plane pass- ;ing through ,the axis -()f the drive shafts l2 .and .13, although it may .be otherwise divided, as for instance, al ga plane passing through .the .engi ne shaft axis L0; In the particular embodiment here sheyvn, the plane of division passes .axis of the two drive :shafts The en ine Shaft -|-,l1 may be either the crank shaft of the engine or an extension thereof or it may be a driven shaft extending from a reducing gear mechanism 'rectl-y associated with the .en- :g-ine or ass ount r haI-t associated with and driven by the 3aft, depending upon the type of engine n d, that is, depending on whether the engine is designed for and equipped with" reducing gearing or counter-shaft or whether it is a direct drive, In any event, however, the shaftilfl is the shaft through which the enginedelivers the power. I

The shaft H1 is preferably splined as at H, and telescopically superimposed upon this spline portion is a correspondingly splined sleeve 18 which is thereby tkeyed tothe shaft Ill against relative '22, just as the inner centering bushing- ;l;9.. are

both snugly fitted over the cylindrical portions of the shaft Ill, so that they will accurately center and keep centered the member I8 in relation to the shaft Ill. The outer conical centering bushing 22 may be made of two halves or it ma be split into two or more than two segments, and may beiprovided with .anlinternalrannular groove 23 adapted to receive the outwardly extending lateral flange 24 of the clamping nut or threaded tightening sleeve 25 which is threaded onto the outer threaded portion 25 of the shaft I0. By

drawing {the nut or sleeve 25 onto the outer threaded end Zliof the shaft H], the outer conical centering .bushing 22 is driven tightly into the :conical endaof-the member [8, thereby to tighten it and center it atcthe same time.

The sleeve L8 is in effect a planet arm or spider carrying one or more radially extending spindles 33 on which are mounted similar bevelled planet pinions 34. Forthe purposes of reducing the contact pressure .on the teeth, .a number of such spindles 13.3 and pinions $34 are. provided, dis- .tributed around the circumference at equal I distances. JIn theconstruction shown, two or-more such spindles and pinions maybe carried by the .member 1-3. Each of the pinions 34 issupported .fastened tightly between the shoulder-at the root .of the spindle 33 .and the nut .38. The-outer ,or

movable racesof .these bearings are held between the inwardly extending flange 39 of the pinion hub and the outwardly expansible spring looking ring expanded into the internal groove 4| in the .hub of thepinion. The bearings 35 and 36 are preferably so arranged as to take radial as well as axial thrust because-the power is transmitted through surfaces inclined to the axis by reason of the .fact that the :pinion is bevelled. Thus, one or both of the bearings -35 and 36 may be combined thrust and radial bearings, as for instance, the bearing 36 which is shown as being of the combined thrust and radial type. If desired, however, one or two roller, type bearings may be used; was forinstance, bevel roller bearings with .the effective angle of the bevel inclinedgenerally the same as the inclination of the bevel gear.

The planet pinions 34 are constantly in mesh with a pair. of opposed bevel gears 43 and 44, respectively, which are arranged generally coaxially with respect .to the axis of the shaft l0.

Each of the bevel gears 43 and 44 is carried 'on similar hubs and 46, whosetubular axial extensions 46a and 4-7, respectively, carry the, bevel gears 43 and. 44-, and whose basal portions 45 and 46 have formed thereon similar bevel gears 48 and 49.

The basal portions 45 and 46 0f the bevel gear hubs are journalled upon similar stationary tubular spindles50 and 5|, respectively, mounted in the opposite ends of the housing members I la and -l lb, respectively.

Each of the tubular spindles 50 and 5| is provided at its inner end with an outwardly extending flange 52 and 53,- respectively, and is threaded at its outer end as at 54 and 55, to receive the nut 55 and 32, respectively. The tubular spindles 53 and 5! fit closely in the openings 5.! and 58,111 the housing members H-a; and Hb, respectively, and between the respective flanges 52 and 53 on one hand and the housing on the other hand, pairs of Similar ball bearings or other anti-friction bearings 59 and 60 and 6| and 62 are mounted, with spacer rings; 63 and 54 intermediate the inner races of the ball bearings. By tightening the nuts '56 and 32, the stationary or inner races of the bearings are held rigidly to the frame. One of the ball bearings in each pair, as for instance, the ball bearing 60 and the ball bearing 6| may be of the combined radial and thrust type for resisting or bearing the axial component of the forces exerted upon the bevelgears 43 and 44 and upon the bevel gears 48 and 43.

A pair of similar driven bevel gears 55 and B are arranged opposed to each other and with their axes slightly spaced in opposite directions from the axis of the spindles 33 or spaced slightly in opposite directions from the plane passing through the axis of the spindles 33, so that one of the gears 65 meshes with the gear 48 while the other gear 66 meshes with the gear 49. a

The hubs 61 and 63, respectively, of the gears 65 and B6 are journalled in similar pairs of ball bearings or other anti-friction bearings 60 and III and II and I2, the outer races of which are held between the two separable halves II a and II-b of the housing II, while the inner races of which are held between the shoulder on the respective hubs and an outer shoulder-on the shafts I2 and I3 which pass through the gear hubs and which are splined thereto by a series of circumferentially distributed splines I3 and I4, respectively. Nuts 75 and I6 serve to lock the shafts in the gear hubs against axial displacement.

When the resistance to turning the shafts I2 and I3 is equal, then there will be no relative motion between the planet pinions 34 and the gears 43 and and 48 and 49. They will all turn together as though one unit with the" shaft III. Therefore, under conditions of equal resistance to turning in the shafts I2 and I3, the two shafts l2 and I3 will rotate together in the same direction and at the same speed.

Should there be any inequality, however, in the resistance offered by the shafts I2 and 13 to turning, then the two gears 43 and 44 and the corresponding gears 48and 49 will be rotated in opposite directions relative to each other, although still rotating in the same general direction; that is, they will be rotated in the same direction but at difierent speeds, this difference being brought about by the rotation of the planet pinions34. Under these conditions, therefore, the two shafts l2 and I3 will likewise be rotated in Opposite directions relative to each other but withboth of them still rotating in the same direction but, at

different speeds. This speed difference or difference in rotational speed will be just sufficient to equalize the torque on the two shafts.

The shaft It! may also be supported in the housing l I by a ball bearing 'Ilheld between the flange I8 on the shaft and the nut I9 thereon.

The slightly offset shafts I2 and I3 are extended upwardly in the manner indicated in Figure 4, at an angle more or less corresponding to the upward inclination of the two cantilever arms 2 and 3 (Figure2) through which these shaft-s extend. Universal joints of conventional type may be provided to permit deflection without bending stresses in the shafts.

The outer ends of the cantilever arms 2 and 3 terminate in or have attached thereto similar housings I9 and 80, illustrated particularly in Figure 6, with the housing preferably formed of a lower and an upper half 8| and 32 respectively,

which are separable along the parting line 83 6 where they may be held together by a series of peripherally distributed bolts or screws 84.

Arranged in a generally upright position within the housing 30, is a hollow rotor hub spindle 85 supported at its two extremes by ball bearings 86and 8'! or other suitable anti-friction bearings such'as roller bearings or the like, one or both of which are of the combined radial and thrust type so as to resist the lift exerted in an upright or axial direction. In the particular illustration shown, the lower bearing 81 shown is of the combined radial and thrust type whose outer race is held in the portion 38 of the lower housing member 8 I.

The ends of the shafts I2 and I3 are mounted in similar bearings 89 and carry similar helical bevel pinions 33 which are constantly in mesh with corresponding driven helical bevel gears 5 whose hubs 92 are journalled on ball bearings or other anti-friction bearings 93 and 94 upon the outer cylindrical surface of the hollow tubular rotor hub spindle 85. The gear 9I is also provided with an internally splined cylindrical flange or drum 95, within which is mounted and to which is splined the externally splined outer race 93 of a roller type or any other suitable type of overrunning clutch. A corresponding innerrace ill of the overrunning clutch is similarly splined at 98 to the outer surface of the tubular rotor hub spindle 85, and between the two races 96 and 91 a series of \ciroumferentially distributed rollers 39' are interposed and held in place between annular plates I and IM, which may be pinned, screwed or riveted together intermediate therollers 99 merely to act as a cage or retainerv for retaining the rollers 39. The inclination of the eccentric surfaces or cam surfaces of the over running clutch is so arranged that when the speed of the rotor hub spindle would tend to lag behind the speed of the shaft I3, the clutch rollers 99 will engage and will permit the shaft- I3 (through the pinion 30 and gear iii) to drive the rotor hub spindle 35 and the rotor fixed speed ratio determined by the gear ratio between the parts, while if the driving shaft 53 slowed down below the then speed of the rotor or if the rotor picked up speed beyond the then corresponding speed of the driving shaft I3, the clutch would release and the rotor would rotate free of the drive shaft I3.

By this means, any failure in the transmission permits the rotors to perform in an autorotative manner without any hindrance from any gearing and it also permits the autorotative operation of the rotors for various maneuvers where it may be desirable to auto-rotate instead of power-drive the rotors. 'j

A brake drum I39 may be splined to the rotor hub spindle as at HI), and may be surrounded by an externally contracting brake bend III operated through any suitable brake band contracting or expanding means mounted in the housing member 8! and having external cable control or other suitable control extending into the cockpit orhaving suitable control means extending into the cockpit cantilever arms I and 2.

To the rotor housing member 8|, housing extension I I 2 is secured, as for instance by the bolts II3, said housing extension HZ being coaxially disposed with respect to the rotor hub spindle 85.

Within the lower housing extension H2, the cyclic pitch change control means (to be described more in detail hereinafter) are mounted.

The upper end of the rotor hub spindle 85 carries a number of blade attachment lugs H4 depending on the number of blades in the rotor. In

therarticular embodiment of the-invention here shown, a three-blade rotor :is contemplated, although. this may be increased or decreased, A thrice-bladed rotonhowever, has been found preferable-in some respects.

Eachiof. the blade attachment lugs is offs et'from the radial location, so that in a mean or cruising powerroperation, the blade axis is in line with the centerof each lug, as shown particularly in Figure 7' (the blades being arranged for lag about a generally upright lag pivot, in "a manner to be described more in detail hereinafter). By this disposition of the blade attachment lugs I I4, side thrust and bending moment on the flapping pivots I;I'-5is reduced to a minimum.

'To-each of the blade attachment lugs II4, a flapping pivot member H6 is pivotally secured by means of the hollow tubular (or solid) pivot II5. This permits the free flap of the blades for coning purposes.

Set screws II'-'I extended through the lugs II4 may bearranged to keep the hollow pivot pins I I5 fast in the lugs I-I4 so that the pivot member I It will oscillate in relation to the pivot pins.

To the pivot or hinge member I I6, the upright pivot housing members I I8 and I I9 are secured by bolts I26 or by other suitable means, or one of these housing members (II 8 and, H9) may be formed integrally with the hinge member I I6.

Within one of the two housing members H8 and H9, as for instance in the lower one as in the embodiment shown in Figure 6, an eccentric ring I2I is mounted with needle type roller bearing I22 interposed for freer rotation, and within the eccentric ring I2I, but eccentrically with respect thereto one end I23 of an offset upright pivot member I24 is journalled by means of the selfaligning ball bearing I25 (or other self-aligning anti-friction bearing such as a self-aligning roller hearing). The other end I26 of this same offset pivot member I24 is similarly journalled in the other housing member II8 by self-aligning ball bearin I21 (or other similar self-aligning bearme).

By this means (and without any displacement of the eccentric ring I2I) the pitch of the blade I28 will be varied as it swings to and fro about the offset pivot axes. The blade is so arranged that in auto-rotative (or power-free) operation, the blade pitch will be a small angle and one best suitable for auto-rotative operation, and so that as the blade lags upon the application of power, the blade angle or pitch will be increased more or less in proportion to the amount of the lag.

Accordingly, the blade root socket I29, in which the blade root I30 is secured in the manner indicated in Figure 6, is preferably formed of two halves separable along a median plane indicated by the line I3I and preferably held together by a series of bolts I32. The blade root socket I29 is clamped tight about a laterally projecting annular rib I33 which extends around the center of the combined pivot member I24, so that the blade root socket I29 will be clamped tightly to the pivot member I24 and so as to force all relative rotation to be through the journalled ends I23 and I26 of the pivot I24.

A rearward extension I34 on the blade root socket member I29 may serve as a limiting means for the displacement of the blade about the axis of the pivot I24, as for instance by placing more or less rigid or resilient abutments on the housing H8 or II9 on either side of the extension I34, so as to limit the movement thereof within de ired limits.

Y By the foregoing means, an automatic pitch change is effected which is responsive to the power nput .or-which is responsive to the-amount of torque delivered from the engine to therotor at any time, increasing with the increase-of such torqueand decreasing with the decrease of such torque until it reaches the auto-rotative angleor pitch in the power-free condition when the lag is reduced to a minimum or substantially zero (that is, the condition in which the blade: axis will be more or less approximately radially di posed with respect to the rotor hub axis or will more or less approximately lie in a plane which includes the rotor hub axis).

To the eccentric ring I2I, a lever arm- I:36 is secured by bolts I3 which may extend through suitable slots in theoute-r casing H9, which surrounds the. eccentric ring (as shown in Figure 7) or the lever I36 may extend around the outer housing H9 and engage the eccentricwring; .12I from the inside; The end I38 of the lever I36 is located substantially in alignment with the axis of the flapping pivot pin lI-5, so that the end I38 of the lever I36 will always remain in substantially the same place in reference to. the rotor hub irrespective of the up and down flapping of the blade.

.A cover plate or supporting plate or member I 39 is superimposed upon the lugs H4 and bolted thereto by means of the bolts I40. may replace the set screws III heretoforementioned, that is the bolts I 43 may serve as set screws. To the underside of' the supporting member plate I39, a bell crank member I4! is pivoted around a generally upright pivot I42, having an arm I43 extending towards the lever I36 and overlapping the end I38 thereof and having another arm I44 extending towards the center of the rotor hub as indicated iii-Figures 6 and. 7.

The lever arm I43 of the bell crank" lever is preferably provided with a'roller I45-for contacting the end I38 of the lever I 36. The lever I44 of the bell crank MI is provided with a similar roller I46 which bears against and, is adapted,- to ride the spherical cam member I-4-I near the axis of the rotor hub. By displacing the spherical cam M! from the geometric" axis of the rotor hub (in a manner to be described hereinafter), each of the offset pivot members I24 maybe correspondingly deflected cyclically to vary the pitch of each blade; the direction of the deflection of the spherical cam member I41 determining the azimuth of thepitch cycle. By this means, the thrust vector of the rotor may be inclined by an amount corresponding to the amount of the displacement of the cam from. the rotor hub axis while the direction of such. displacement determines the direction or inclination of the thrust vector of the rotor. I V

In the particular embodiment of my invention herein shown, the displacement of the cam member I41 is effected by pivoting said cam member as at I 48 to an upright rotatable member I49 with which it will therefore rotate in unison, and providing a bell crank arm I50 connected through a suitable link, I5I to a vertically adjustable ring I52, so that the upward and downward movement of the ring I52 will determine the amount' of the cam displacement in relation to the rotor hub axis while the rotation of the member I49 will determine the direction of such displacement.

The member I49 has its upper portion journalled in the ring I52 as at I53, while its lower These boltsenlarged end is similarly journalled in the lower end I54 of the tubular member I55; the upper end of the tubular member I55 being in turn journalled in and being freely rotatable in relation to the interior of the tubular rotor hub spindle 85, as at I51, while the lower end I54 of the tubular member I55 is vertically slidable in the stationary lower extension II2 of the housing member 8! but keyed thereto (by a suitable key I58) against relative rotation. The lower cylindrical wall of the housing extension H2 is surrounded by an operating ring I59 which is revoluble in relation thereto. A series of circumferentially distributed elongated slots I55 are extended through the cylindrical part of the housing extension II2; said slots being all arranged in the same common plane. Opposite these slots I55, a similar but inclined series of slots II are provided in the lower portion I54 of the cylindrical sleeve I55. A series of pin members I52 are threadedly anchored in the outer control ring or operating ring I59 with their smooth shanks extending through the outer plane slots I55 in the stationary housing extension H2 and into the inclined slots I5I in the lower cylindrical part I 54 of the cylindrical sleeve I55. As the lower part I54 of the cylindrical sleeve I55 is vertically movable but otherwise keyed to the stationary housing extension H2- (agalnst rotation) any rotational displacement of the ring I59 around the housing extension II 2 will cause the sleeve I55 to be displaced in an up or down direction. This up and down movement is transmitted to the ring I52 which is held between a shoulder I53 in the upper end of the sleeve I55 and a threaded retaining ring or nut I54 threaded into the upper end of said sleeve I55, The ring I52 is freely rotatable in relation to the sleeve I55, however, so that it may rotate with the angular adjusting member I49. Thus, the angular position of the ring I52 is determined by the member I49, while its vertical position is determined by the sleeve I55 (independently of the member I49).

To the lower enlarged end I55 of the angular adjusting member I49, a ring or ldise I55 is secured by means of bolts I51, which together with the webs I58 and I59 and the intermediate ring I15, forms a sheave over which a control cable I1I extends, and through whichthe direction of the member I49 and hence the direction of the displacement of the cam I41 may be controlled. The position of the control ring I59 on the other hand may be controlledby two tension members I 12 fastened to suitable lever arms extending from the ring I59 (which lever arms are not shown). Preferably, two opposite arms I and I15 are provided on the control ring I59 in the manner indicated in the schematic drawing of the controls in Figure 8 with cables I12 and I13 extending therefrom into the fuselage.

In the embodiment of the invention herein shown, the cables I12 and I13 which control the magnitude of the cyclic pitch change are connected or attached to any conventional control stick I11 in a fore and aft direction in such a manner that when the stick I11 is pulled back in the direction of the arrow I18, the displacement of both spherical cams I41 (that is, in each of the two rotors) will be increased so as successively to incline the thrust vector of the rotors from their normal upright direction (as when hovering) and so that when the stick is moved forward in the direction of the arrow I 19, the inclination of the "10 thrust vector from the hovering position will be increased similarly in the opposite direction.

In order that the cyclic pitch change may be directed uniformly or differentially, at will, the cables I12 and I13 are caused to pass over a series of stationary idle pulleys I85, I 8i I82 and I83 suitably supported in the fuselage, and a series of floating idle pulleys I84, I85 and I85 which are carried by a movable or floating plate I81, whose position is determined by the supplemental rudder control cables I88 and I89, which pass over idle pulleys I and I9I, respectively, and are then connected with the main rudder cables I92 and I93 which are connected with the conventional food pedals'or treadles I94 and I95 and together with the intervening cables I95 and pulleys I91 and I98, serve to control the rudder 5 heretofore described. By moving the rudder pedals I94 or I95 (difierentially) the disc or support I 85 is moved backward or forward, thereby causing a differential operation of' the two cams I41 in the two rotors, because the'forward movement of the disc, I85 (by pressing on the pedal I95) causes both cables I12 to be shortened and causes both cables I13 to be correspondingly lengthened so that the two control rings I59 are rotated in oppositedirections. Th same takes place when the opposite pedal I94 is depressed but the members merely rotate in the reverse direction.

The direct control cable IN is caused to make acomplete circuit around the two sheaves I15 and over the pulleys 2'55, 25I, 252 and 253 to the control stick I11 in such a manner as to be moved by the lateral motion of the same. Thus, the lateral motion of the stick I11 will cause the direction of greatest pitch change or the azimuth of the cyclic pitch change to be directed in the direction opposite to that in which the stick is moved,

and by an amount corresponding to the displace ment of the stick, so that the thrust of the rotors will be in the same direction as that in which the stick is moved.

Thus, the direction of the propulsive thrust is controlled by the lateral displacement of the rotation of the cam I41 is sufficient to provide the lateral wheels 251 and 258; the fore and aft wheels being, carried by the fuselage uponsuitable hydraulic or other resilient supports, while the lateral wheels 251 and 258 are preferably carried by the cantilever arms 2 and 3, also through suitable hydraulic or other resilient supports.

In place of the cables I12 and I13 applied to the arms I15 and I15, 2. more or less rigid rod may be used with but a single arm, the rod acte ing eitherin tension or compression; that is, operating by push and pull. Likewise, if desired, a single cable may be used supported by a spring of sufiicient strength. Instead of the means shown iii Figure is for d fiereritia iy ve ting t-iie amplitude oi the pitch change iii the twp retort, hydraulic means may be used; as hydraulic means "may also be used for transmitting both the amplitudecontrol as wen as the aziihuth control from the fus lage to the "rotor hubs, Thus, the amplitudechahg ih'g means sheen in Figure 6 may be hydraulically operated v general man r ei indicated in my eopeiiemg application seiiai No. 242,053, eate'nt; No, 2364,0913 of December 5, 194ji, wifiu'e the ae'ii miti changing means may likewise be hydraulically controlled by suitable hydraul c actuating cyl inders', pistons and transmission liiies ap'plied to rotate the members I70. 7 v azimuth control means ma then be hydrauli cally inter' -relat ed throughsuitable i'lali es to effeet the amplitude of the pitch change in the two rotors either siihilarlyjor differentially.

As can be seen particularly {rem Figures land 4, the rotors 12a rotate bppo's'ite1y; the direction of rotation of the rotors being sliCh that when Viewed in top plan, from adjacent therea'r of the machine, the left-hand i 'ot'or rotates counter'clockwise and the right han'd rotor 'clo'ckwise.

As can be s'eeii particularly from Figure 2 the outer rearwardly-moving blades of the rotors I28 are inclined upwardly from their hubs while the inner forwardly-moving blades are inclined downwardly from their hubs. Thiis, as a result of the aerodynamic and inertial forces on the articulated blades, the composite lift lines 'or effective axes of rotation of the two rotbrs are inclined upward and inward so as to introduce a natural dihedral effect during translational flight. g

The present invention may be embodied in other specific forms without departing froiii the spirit or essential attributes thereef, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being had tti the appended claims rather than to the foi'goihgdescription to indicate the scope of the invention.

Having thus described the invention, What i S hereby claimed as new and desired to be secured by LettersPatent is: y

1; A helicopter including twe lift iota'rs havmg spatially-separated rotation axes, generally upright'piyo'ts mounting the blades thereof for lagging in response to driving t ')rq"ue-, iiieahs mounting said blades for pitch change; and means including self-aligning bearings associated with the pivots for correlating pitch changeswith lag changes. 7 i

2; A helicopter including a lifting rotor hayg in'g a drii ing' hub, a blade attached to Said through generally upright and horizontal pivots, a tiltabl'e mounting for said upright pivot, an eccentric meinber mountd in said hub, means for controllably varying the eccentricity and the 'aLzi muth of said eccentricmember, and means ateratively interconnecting said eccentric with said tiltably mounted 'p'iyot whereb said eccentric controls the tilt of said pivot. i

3. In 'a helicopter supported by tWb rdtii'rs' having spatially separated rotation axes, cohtro'l means including means for impartin'gcyclicpitch change'to the blades in each rotor, means for varying the azimuth of said cyclic pitch change, means for varying the amplitude of said Cyclic pitch change, cable means interconnecting said azimuth change means with the lateral motion The amplitude and oi a 'ceitro'l fstick, table means interconne ting amplitude chailgel means with the longitudi-i 'ial motif n of said manual control stick, a fleeting frame carrying pulleys cee ert ting with saiaeinaiittiue ehange cable means, and cable n eai seoniie'ct n said floating frame to entrol pedalsfor acting differentially on said amplitude changing means.

4'. a helicop er su ported by two rotorshavihg 'spatiallyfs'eearated rotation axes, control means including means for imparting cy'cl'ic' pitch change to the blades in each rotor, means for varying the. azimuth of said 'cycl'ic 131' h change, mean for varying the amplitude (if s in cyclic; pitch hange, inean'sinterconne ct ing js i'd azimuth change means with the lateral motion of a ifrianual control, means interconnecting said amplitude chang means with the lohgit'udihal motion of said 'hianual control, foot controls'ai d means operatiifely interconnecting fs'a'i d ampli ti' de angin means with said foot controls, whereby the amplitude changing means will be caused to act differentially upon the operation of said foot controls. 7 v I 5. A helicopter including a fuselage having a pair of laterally extending pylons exten ing 'froin the fuselage at a point below the center of gravity of the helicopter, a lift rotor carried by each of said pylonaan engine in the fuselage for driv ing said rotors; said 'p'ylons' presenting a substantial aerod namic resistance in a verticalgdirec tion in rapidly moving Zones of the slip streams cfthe rotors and at a point below the center of gravity of the-helicopter. p

e. A helibcpterincluding a fuselage, a rotor,

engine fer driving the same; and means he heath said rotor and in a rapidly moving zone of the slip stream thereof and beneath the center of ra ity at the helicopter for im osing drag beneath the center "of gravity of the helicopter, thereby to stabilize the helicopter.

' HAVILAND H. PLATT;

REFERENCES CITED The renewing references are at record'ih the file bf this patent:

UNITED STATES PATENTS t D'iai l Q82 Burri'er Augflki; 19 20 133mm; Mott June 7, 1921 3013 W ii Nov; 3, i931 McGuire Mans, 1932' 1;91 0;f5 2Q i p erva May 23,1933 1,9195089 Breguet .i. July is; 1933 "1,942,888 West Jane; 1934 1g95'7g8'13 Wilford May 8,1934 232 572 campbeii June 15, 1943 2,337,570 Pullin Dec. 28, 1943 FOREIGN PATENTS Nii'n lo'e'r, Country 7 ,Date, $21 162 Great Britain Sept. 29, 1999 1274's a ea Bri in Au 2 .1921? 499,073 Great Britain "Jan. 18, 1939 QTHiiit iteeeaeitchs "The Fe'cke wel f- H'ehcbpter. Publication: Flight, pages 380 383-,Tinc1u'sive, of Apri1"21,,l38; s. 1 1 V ,,JanesiAll the jWorlds Aircraft, 1937; page 1720. t 

